Oximes are useful as organic intermediates and for various other applications. For example, they undergo the Beckmann rearrangement, can be alkoxylated and hydrogenated, and are useful as lubrication additives and anti-icing additives. Some oximes can be converted to synthetic fibers (i.e. cyclohexanone oxime can be converted into caprolactam, an intermediate for the commercial preparation of Nylon 6).
Paraffinone oximes have been prepared by the base catalyzed reaction of ketones with hydroxylamine salts and more recently by the photolytic nitrosation of normal paraffins. Both of these synthetic methods can produce a crude product which contains substantial quantities of contaminants boiling close to or overlapping the boiling points with the oxime product. Most of these impurities encountered in both processes are aldehydes or ketones (which are referred to generically as carbonyl-type impurities), while in the photolytic process gem-nitrosochlorides and gem-nitrosochloride condensation products can also cause separation problems. In any event, conventional distillation under high vacuum of the crude oxime obtained through photolytic nitrosation fails to produce high purity (i.e., 95 percent or higher) products free from ketone impurities. Examples 1 and 2 provide evidence of this anomaly.
In view of the separation difficulties presented by these impurities, there is a need for a purification procedure directed to the purification of paraffinone oximes containing substantial quantities of carbonyl-type and organic chlorine impurities. Particularly useful would be a simple treatment whichh would utilize as starting material a crude oxime product derived from the photolytic nitrosation of n-paraffins such as disclosed in U.S. Pat. No. 3,578,575, and which contains substantial quantities of carbonyl-type and/or organic chlorine impurities. Desirably, the purification procedure would utilize the 95 percent and lower oxime content product of the above application and convert it to a product of 98 percent and higher oxime content. Ideally, the novel process would be relatively inexpensive, would require no particular expertise and would utilize commercially available equipment.